Inline diff output comes out very narrow

I've just setup Lifewire Diff on Drupal 5.11 and found an problem with the inline diff output coming out very narrow, 4 characters wide when using IE6.

If I resize the browser, it will layout correctly.

I'm using the bluemarine theme, and have found that changing the theme does sometimes fix the problem.

I assume it is a table layout problem, but being new to Drupal, wasn't sure where to start looking.

Thanks in advance for any help.